The present invention generally pertains to optical scanning systems and is particularly directed to a mirror scanning assembly for use in scanning a code symbol consisting of a combination of spaced parallel bars affixed to an object.
A typical scanning system of this type includes a housing with a panel for defining a scanning region adjacent the panel for receiving objects having a bar code symbol, and a light source, such as a laser, for providing a light beam; and an optical system for scanning the light beam in a predetermined pattern throughout the defined scanning region. The system also includes a detection system for detecting light having at least a predetermined intensity reflected from the bar code symbols and for providing an electrical signal in response to detection of such reflected light; and an optical system for directing light from the scanned light beam that is reflected from the code symbol on a received object to the detection system.
These systems are useful in reading bar code symbols such as the Universal Product Code (UPC) code symbols that are affixed to many packaged grocery items. UPC code symbols consist of parallel bars having various widths and spacings. The electrical signals provided by the detection system in response to scanning the code symbol are provided to a data processing system which provides various functions in relation to the information represented by the electrical signal, such as registering and displaying the price of the item bearing the code symbol and adjusting inventory records concerning such items.
One consideration in using scanning systems of this type is the orientation of the code symbol within the scanning region defined by the panel so as to enable the full code symbol to be scanned by the light beam. In many prior art scanning systems, the code symbol must be precisely oriented within the defined scanning region in relation to the panel. The time consumed in precisely aligning the code symbol delays the scanning of a large number of items. One prior system that does not require precise orientation has a panel which defines the scanning region for receiving objects bearing a code symbol which includes light transmissive areas defining a "bar X " or double X scanning pattern. The present invention deals with a bar scanning mirror assembly for scanning double X bar patterns.
Typical prior art U.S. patents which show rotatable mirror assemblies can be seen in the Starkweather Pat. No. 3,944,323 for a variable spot size scanning system having a rotatable faceted mirror assembly with arcuate mirrors mounted thereto and in the Jeffery et al. Pat. No. 4,043,632 for a scanning polygon mirror assembly having adjustable mirrors mounted thereto. In the U.S. patent to Runciman No. 3,845,298 an optical scanning device has a rotating drum carrying a plurality of orthogonal planar mirrors. In the Bohn et al. Pat. No. 3,040,627 a rotating mirror assembly has one embodiment with cylindrical curvatures on the face of the mirrors. In the U.S. Pat. to Person No. 3,843,226, an apparatus for periodical parallel displacement of at least one parallel beam is provided while the Hayosh et al. Pat. No. 3,988,573 is a three line scanner for bar code symbols showing a typical bar code scanner having a rotatable mirror assembly therein. In U.S. Pat. No. 4,093,865 to Nickl, a typical double X bar pattern bar scanner is shown having a conventional rotating mirror scanner assembly with faceted mirrors rotated on an electric motor. The present invention is designed for use in a double X bar pattern scanner and specifically to the rotating mirror assembly for the scanner in which the rotating mirror assembly has shaped mirrors for directing the scanning and the return beam of a laser in a double x laser scanner.